1. Field of the Invention
The present invention relates to a magnetic tape cassette used in a video tape recorder (hereinafter, referred to as VTR).
2. Description of the Prior Art
The conventional magnetic tape cassettes used in the VTR are classified into two types: the VHS system and the beta system. In either system, a casing assembly is fabricated so as to hold a magnetic tape, a pair of feeding and winding reels on which the magnetic tape is wound. FIG. 1 illustrates the conventional magnetic tape cassette for the VHS system. A magnetic tape (3) and a pair of feeding and winding reels (4), (5) for winding the magnetic tape (3) are held in a casing assembly comprising an upper half casing (1) and a lower half casing (2). Tape guides (6), (7) and (8) for guiding the magnetic tape (3) and a tape pade (9) are provided between the feeding reel (4) and the winding reel (5) in the running passage for the magnetic tape (3) in front of the casing assembly so that the magnetic tape (3) runs from the feeding reel side to the winding reel side along the arrow direction (A) while the magnetic tape is sequentially brought into contact with these parts (6) to (9). A guard panel (10) is pivotally supported in the front of the casing assembly so as to cover the magnetic tape (3).
As shown in FIGS. 2(A) to 2(C), the feeding reel (4) and the winding reel (5) respectively comprises a circular reel hub (11), a cylindrical axial part (12) to which the driving shaft of the VTR (not shown) is connected, a cylindrical magnetic-tape winding core (13) having a larger diameter than the axial part (12), said axial part (12) and said winding core being formed in coaxial with the circular reel hub (11), and reinforcing ribs (14) which radially extend between the axial part (12) and the magnetic-tape winding core (13) to connect them.
A plurality of reel driving ribs (15) with which the driving shaft of the VTR engages are formed with a suitable spacing on the surface of the inner diameter of the axial part (12). A recessed portion (16) is formed at a part of the outer periphery of the magnetic-tape winding core (13) so that the end portion of the magnetic tape (3) is clamped by the recessed portion and a fitting element (17) which is inserted into the recessed portion (16). A through hole (18) communicating with the reel driving side (B) of the core is formed in the position corresponding to the end portion of the fitting element (17) whereby the fitting element (17) can be forcibly removed from the recessed portion (16) by inserting a jig (19) into the through hole (18) from the opening of the reel driving side of the core as shown in FIG. 3. The through hole (18) is formed at the center of the recessed portion (16) and the position of the hole (18) coincides with that of one of the reel driving ribs (15).
The feeding reel (4) and the winding reel (5) have exactly the same structure as described above. It is, therefore, unnecessary to distinguish both the reels from each other in the assembling operation. However, when it is necessary to separate the thickness of the feeding reel (4) from that of the winding reel (5), and hence distinguishing of the feeding reel (4) from the winding reel (5) is required, it is difficult to distinguish the feeding reel (4) from the winding reel (5) because the other dimensions are completely the same thereby causing erroneous assembling operations.
It can be considered to distingush the reels (4) and (5) by changing the structure and the shape of the reels (4), (5). However, it is not practically applicable because they have different configurations whereby it is not easy to detect the difference and further functional problems may result by the change of design.